The invention relates to a fan for a cooling system of a motor vehicle with a closed impeller having several radial vanes disposed between an impeller bottom and a cover disk, wherein the inner contour of the radial vanes is defined by their vane leading edges and the outer contour of the radial vanes by their vane trailing edges.
A fan for a cooling system of a motor vehicle is known from. German Patent Publication DE 25 30 742 C3, which has a radial impeller disposed, viewed in the direction of air flow, in back of a heat exchanger of a coolant circuit of the cooling system of the motor vehicle. The radial impeller is embodied to be closed and has a plurality of radial vanes disposed between a cover disk and an impeller bottom. The radial impeller is driven via an interposed friction clutch when the vehicle is stopped or moving slowly in order to assure a sufficient flow through the heat exchanger even without a sufficient air flow from movement of the vehicle. The inner contour of the radial vanes is defined by the vane leading edges extending parallel with respect to the axis of rotation, the outer contour by vane trailing edges extending correspondingly parallel.
It is an object of the present invention to provide a fan of the above-mentioned type which is improved with respect to its sturdiness and is designed advantageously with respect to flow technology.
These and other objects have been attained according to preferred embodiments of the invention by providing a fan for a cooling system of a motor vehicle with a closed impeller having a plurality of radial vanes disposed between an impeller bottom and a cover disk, the radial vanes extending in a generally radial direction with respect to an axis of rotation of the impeller, an inner contour of the vanes being defined by leading edges of the vanes and an outer contour of the vanes being defined by trailing edges of the vanes, wherein each of an exterior diameter of the outer contour of the radial vanes and an interior diameter of the inner contour of the radial vanes decrease in a direction from the cover disk toward the impeller bottom.
The bending moment caused by centrifugal forces acting on the radial vanes impairs the sturdiness of the vanes, and is reduced by orienting the radial vanes essentially in the radial direction. Furthermore the air flow against the radial vanes is improved by orienting the vanes in this manner. In comparison with the prior art, approximately the same advantageous air flow rate is achieved.
In one preferred embodiment of the invention, the vane bases of the radial vanes are inclined opposite to the direction of rotation. Preferably the inclination is less than 30.degree. with respect to the radial direction. The flow losses in the vane channel are reduced by the inclination of the radial vanes.
In a further advantageous embodiment of the invention, a plurality of auxiliary vanes are disposed on a curved cover disk intake, distributed over its circumference, which project into the area of the radial vanes and extend across the radial height of the curved cover disk intake. As a result, the flow conditions are improved, in particular in the cover disk intake forming the outer wall between the cover disk and the intake nozzle. An improved aspirating flow is achieved.
In a further advantageous embodiment of the invention, the auxiliary vanes are inclined opposite to the direction of rotation of the radial impeller and/or curved in the direction of rotation. This embodiment leads to a reduction of the flow losses in the area of the cover disk intake.
In a further advantageous embodiment of the invention, the cover disk, the vanes and the impeller bottom are made in one piece of a plastic material, and a separate air guide ring, which interacts with a stationary intake nozzle, is provided in the area of the cover disk intake. Because of an unmolding requirement from an appropriate injection molding tool, it is not possible, when the radial impeller is made of a plastic material, to also produce the curved cover disk intake in one piece with the impeller. In order to achieve satisfactory flow conditions in spite of this, a separate air guide ring has been provided in a simple manner.
In a further embodiment of the invention, the radial vanes are curved in the direction of rotation of the radial impeller with a constant radius of curvature with respect to the radial vane extension, respectively beginning at a vane base starting from the impeller bottom. This makes possible the removal of the sucker pins when the radial impeller is made of a plastic material.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.